On Thu, Jun 11, 2026 at 01:26:57PM +0200, David Hildenbrand (Arm) wrote: >On 6/11/26 13:07, Sarthak Sharma wrote: >> >> >> On 6/11/26 3:31 PM, David Hildenbrand (Arm) wrote: >>> The droppable test currently relies on creating memory pressure in a >>> child process to trigger dropping the droppable pages. >>> >>> That not only takes a long time on some machines (allocating and filling >>> all that memory), on large machines this will not work as we hardcode the >>> area size to 134217728 bytes. >>> >>> ... further, we rely on timeouts to detect that memory was not dropped, >>> which is really suboptimal. >>> >>> Instead, let's just use MADV_PAGEOUT on a 2 MiB region. MADV_PAGEOUT works >>> with droppable memory even without swap. >>> >>> There is the low chance of MADV_PAGEOUT failing to drop a page because >>> of speculative references. We'll wait 1s and retry 10 times to >>> rule that unlikely case out as best as we can. >>> >>> On a machine without swap: >>> >>> $ ./droppable >>> TAP version 13 >>> 1..1 >>> ok 1 madvise(MADV_PAGEOUT) behavior >>> # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0 >>> >>> Reported-by: Aishwarya TCV <[email protected]> >>> Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily >>> freeable mappings") >>> Signed-off-by: David Hildenbrand (Arm) <[email protected]> >>> --- >> >> I ran this test before and after applying the patch and recorded the >> execution time over 5 runs on an Orion O6 board. >> > >Thanks! > >> Before the patch, average execution time = 3.87 s > >Out of interest, how much memory did your machine have? > >I ran into this myself on a 200gig machine, and there was essentially no >progress ...
Same here ... With the old test, I waited a quite a while and didn't see any progress ... on a 512 GiB machine.
